Electrochemical studies of nickel tris(phenanthroline) in nonaqueous solvents Part II. Electrocatalytic polymerization of activated olefins

Abstract

The electrochemical behavior of Ni(II)(phen)32+ has been investigated in the presence of a series of activated olefins, i.e., those bearing electron withdrawing substituents. Following the two-electron reduction to the Ni(0) state, a ligand exchange reaction occurs with replacement of a phen molecule by the olefin. The equilibrium constants and kinetics of this reaction were evaluated by electrochemical techniques. Further reduction of the Ni-phen-olefin complex takes place in a one-electron reversible reaction to yield a Ni(−I) species, which acts as a polymerization catalyst for excess olefin in solution. An additional study, using a variety of substituted phen derivatives, shows that the electron transfer properties of the Ni-phen-olefin complex are more greatly influenced by the phen ligand than by the olefin. Also the rate of the olefin polymerization reaction can be markedly diminished by the presence of electron withdrawing substituents on the phen ligand. The properties of the Ni-phen complex are compared to those of Ni-macrocyclic ligand complexes and to the organometallic compound, Ni(bipy)(Et)2.